Having conceded four goals to a Championship side -- losing 4-2 to Nottingham Forest in the FA Cup in their last game -- it was imperative that Arsenal displayed some defensive solidity when they faced Chelsea in the Carabao Cup semifinal first leg at Stamford Bridge on Wednesday night.

The 0-0 draw was a creditable result and gives the Gunners every chance of making the Wembley final next month, but as ever with them there's yin and yang to the performance.

Having endured a difficult day at the City Ground, Rob Holding looked much more comfortable in a back three, as did his England under-21 colleague Calum Chambers. With Shkodran Mustafi more or less holding things together in the middle, the trio of central defenders did enough to stop Chelsea from scoring, although there were a few difficult moments here and there.

Either side of half-time the home side had excellent chances, but Cesc Fabregas headed straight at David Ospina, before Andreas Christensen wasted a glorious scoring chance by nodding the ball over the bar. It was the kind of let off Arsene Wenger's side were always going to need given their current defensive frailties, but having been gifted that they defended with commitment and purpose until the final whistle.

Eyebrows were raised before kick-off when it emerged Alexis Sanchez would start on the bench. Despite the Arsenal manager's insistence that his decision was not affected by the reported £20 million bid from Man City for the Chilean, it's impossible to look at it outside of that context.

The 29-year-old is the team's joint leading scorer, and most productive attacking player, but having secured a 0-0 draw against Chelsea in the Premier League back in September with a front three of Danny Welbeck, Alex Iwobi and Alexandre Lacazette, there may well have been some method to the madness.

Yet it's an attacking trio that functions in terms of hard work and covering space -- evidenced by the fact Welbeck ended the game with five defensive clearances, the third most in the team behind Chambers and Mustafi who had nine each -- but one which ultimately did little to threaten the Chelsea goal.

That was the trade off. Wenger knew that and took a gamble knowing a defeat would have seen him more rigorously questioned over the Sanchez decision. His star man eventually came on in place of Lacazette who'd been struggling with illness, but he too could find no way to trouble the opposition defence.

Jack Wilshere has been in good form of late, but is still injury prone. IAN KINGTON/AFP/Getty Images

The other big worry for Wenger was the departure, midway through the first half, of Jack Wilshere. The 26-year-old has reminded people in recent weeks that he's a very talented player, and calls for him to be given a new deal are completely understandable. Unfortunately, we also got a reminder of the other side of Wilshere: his proclivity to injury.

He suffered an ankle sprain when the ball hit his foot, bending it backwards -- and that's a painful for anyone, not just someone with a history of injuries to that area. However, it highlighted the fact that if Arsenal make themselves reliant on Wilshere, they're playing with fire.

His talent and ability means he should be seen as a very solid squad option; someone who can slot into the first-team at any stage, who can add quality and craft to midfield. But if you're banking on him to stay fit after so many seasons which have been punctuated by injury layoffs, it's poor planning.

Wilshere's injury brings Arsenal's midfield options into sharp focus because of the imminent sale of Francis Coquelin to Valencia. With Aaron Ramsey also out injured, it leaves the Gunners quite light in that area, although it seems as if Wenger is willing to let Ainsley Maitland-Niles make the step up into his natural position when he has left-sided defenders Nacho Monreal and Sead Kolasinac back from injury.

All the same, with a semifinal second leg to come, and the possibility of a Europa League trophy still to play for, the Arsenal manager might find himself best served with a foray into the transfer market for some established midfield talent.